Circuit-arrangement for amplifying and separating signals of different frequencies



Dec. 8, 1953 A. J. w. M. VAN OVERBEEK 2,662,128

CIRCUIT-ARRANGEMENT FOR AMPLIFYING AND SEPARATING SIGNALS OF DIFFERENT FREQUENCIES Filed Aug.

iNVENTOR Adricnus Johannes Wilhelmu Marie Von Ove'beek AGENT Patented Dec. 8, 1953 OFFICE CIRCUIT-ARRANGEMENT FOR AMPLIFYIN G AND SEPARATING SIGNALS OF DIFFER- ENT FREQUENCIES Adrianus Johannes Wilhelmus Marie van Overbeek, Eindhoven,

Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application August 7, 1951, Serial No. 240,6(22- Claims priority, application Netherlands August 25, 1950 This invention relates to circuit-arrangements for amplifying and separating signals of different frequencies by means of a tube having at least a cathode, a control grid, a secondaryemission electrode and an anode, wherein the signal oscillations to be separated are supplied to the control grid circuit.

Known television circuits have been used for separating picture signals from sound signals. Therein, it has been proposed to insert a circuit, tuned to the carrier-wave of the picture signals, in the anode circuit of the tube and to insert a circuit tuned to the carrier-wave of the sound signals in the circuit of the secondaryemission electrode. In these known circuit-arrangements, however, it is often diflicult to ensure an effective separation between picture signals and sound signals if the frequencies of the two carrier-waves approach each other.

It is the object of the present invention to provide an extremely simple circuit-arrangement of the aforesaid type, in which an effectual separation is effected for signals of difierent carrierwave frequencies even if these frequencies approach each other. This circuit-arrangement may be used both for separating picture signals and sound signals and line and frame synchronizing action pulses, for removing interference signals in low-frequency amplifiers, for separating quency oscillations in reflex receivers, and for similar purposes.

In this invention a tube of the type described in the preamble is used. A series-connection of two impedances is connected between the anode of the tube and a point of constant potential; the common point of these impedances is connected to the secondary-emission electrode of the tube. A circuit tuned to one of the oscillation frequencies is connected between the junction 7 point of one impedance and the anode and a point of constant potential. The two impedances have such values with respect to the resonance impedance of the tuned circuit that no voltage of this resonant frequency is set up between the secondary-emission electrode and the point of constant potential. The circuit is comparable to a bridge-circuit which is in equilibrium for one of the frequencies to be separated.

In order that the invention may be readily carried into effect, it will now be described in detail with reference to the accompanying drawing, given by way of example, in which:

Fig. 1 shows circuit-arrangement according to the invention, for example, for amplifying intermediatedrequency and audio-fre- 4 Claims. (01. 179-171) I M audio-frequency oscillations in which an interfering signal of a frequency exceeding the range of frequencies to be amplified is required to be eliminated. The signal to be amplified is sup-- plied between terminals I to control grid 3 and cathode 5 of an amplifying tube 4. This tube, furthermore, comprises a screen grid 6' having a positive potential, a secondary-emission electrode 1 and an anode 8. A circuit 9 tuned to the interfering signal is connected in the lead between the anode 8 and the positive terminal I 3 of the supply. Between the seriesconnection of two impedances I0 and II is connected between anode 8 and cathode 5,-and the common point of these impedances is connected to the secondary-emission electrode 1. The amplified voltage is taken from a terminal l4 connected through a capacitor [2 to the secondaryemission electrode 1. Terminal I5 is connected to ground and to the cathode. Control grid 3 is maintained at a given negative bias through use of network 19 connected between cathode 5 and ground.

The described circuit-arrangement operates as follows: The impedance of circuit 9 is very high for the interfering signal which may, for example, have a frequency of 9000 c./s., with the result that the major part of the anode alternating current for this frequency passes through the impedance H). By giving this impedance a suitable value, the current passing through the impedance I!) may be used to balance the alternating current of the secondary-emission electrode passing in the opposite direction, so that no interfering voltage will be produced at terminal M. A circuit-arrangement, wherein the impedances are constituted by resistors I6, I! is shown in Fig. 2, these resistors serving at the same time to feed supply voltage to the secondary-emission electrode. The resistor I6 is adjustable by means of sliding contact I8, so that the resistance value may be conveniently chosen.

If the signal appearing in the circuit 9 shown in Fig. 1 is to be used elsewhere, as in the aforesaid circuit-arrangements for television and for reflex amplification, this circuit may be coupled to an inductor 20, the signals of the second channel being taken from the terminals 2.

What I claim is:

1. Apparatus responsive to an incoming signal having first and second signal components of different frequency for amplifying and separating said signal components therefrom, said apparatus comprising an electron discharge tube having a cathode, a control grid, an anode and a secondary emission electrode, a resonant circuit tuned to the frequency of said first signal component and coupled between the anode of said tube and a point of high constant potential relative to the cathode of said tube, means to supply said incoming signal to the control grid of said tube whereby both signal components appear in amplified form at both the anode a d the secondary emission electrode of said tube, first and second impedances serially connected together between the anode and cathode of the tube, the junction of said impedances being connected to said secondary emission electrode, said impedances having impedance values measured at the frequency of said first signal component at which relative to the corresponding impedance value of said resonant circuit substantially all of said first signal component appears across said resonant circuit and substantially all of said second signal component appears between said junction and the cathode of said tube, means toderive the amplified first signal component from said resonant circuit, and means to derive the amplified second signal component from said junction point.

2. Apparatus as set forth in claim 1 wherein both of said impedances are resistances.

3. Apparatus responsive to an incoming signal having first and second components of different frequency and adapted both to amplify and separate said components, said apparatus comprising an electron discharge tube having a cathode, a control grid, an anode and a secondary emission electrode, means to apply a bias to said cathode relative to ground, a resonant circuit'tuned to the frequency of said first signal component, means to apply a positive potential relative to ground to said anode through said resonant circuit, means to supply said incoming signal between said grid and ground, first and second impedances connected serially between said anode and ground, the junction point of said impedances being connected to said secondary emission electrode, said impedances having values with respect to the frequency of said first component at which relative to the impedance value of said resonant circuit at the same frequency substantially all of said first frequency component is developed across said resonant circuit while substantially all of said second signal component appears between said junction and ground, means to derive the amplified first signal component from said resonant circuit, and means to derive the amplified second signal component from said junction point.

ei- Apparatus, as se forth in im wherei he impedance connect d een sa d ano e nd said secondary emission electrode is constituted by an adjustable resistance element.

ADRIANUS JOHANNES WILHELMTJS MARIE van OVERBEEK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name e-t;

2,235,190 A ma et al- -.-.---V-=.-- Man-.18, 94. .2, 3 J nke let "ea-r June 1. 1. 49

FOREIGN PATENT$ Number Country Date 514,762 Great Britain Nov. 16, 1039 

